1. Field of the Invention
The present invention relates generally to transmissions capable of powering multiple devices from a single drive shaft, and more specifically to pumps and pump transmissions capable of powering an impeller shaft of a fluid pump and at least another device, and particularly to emergency vehicle pumps and transmissions of such variety.
2. Background Information
Transmissions capable of powering a primary device and at least another device are not new. Some transmissions, especially in the automotive or truck areas, include a drive for powering a primary device, such as an axle of the vehicle, and may also include a power take-off, commonly known as a PTO. A PTO device is designed to power an auxiliary device, drawing power from the main drive of the transmission. In some instances an auxiliary device itself might take power off from (or directly connect to) the main transmission, as opposed to coupling with an intermediate PTO device. A PTO device typically attaches to the main transmission and in turn powers an auxiliary device. Typically a transmission includes an internal gear, i.e., a “PTO gear”, to which the auxiliary device or to which the PTO device couples in order for the auxiliary device or the PTO device to be driven.
Pump transmissions, including pump transmissions of the fire-fighting variety have also been designed to power a primary device such as a pump, and at least another device, such as a booster pump or a compressor. One such system includes extending the impeller shaft out the opposite side of the gearbox of a pump transmission. One end of the impeller shaft is engaged with the pump impeller while the opposite end is available for use to power another device. In other systems, an additional gear may be included inside the gearcase to provide a power output. An example of such additional gearing is found in the patent to Hoffman, U.S. Pat. No. 4,587,862, issued May 13, 1986. In Hoffman, an input member 30 alternately powers an output member 32 or a pump shaft 18 by means of a sliding gear 70. A further example of a system that provides additional gearing is found in the patent to Eberhardt, U.S. Pat. No. 5,145,014, where the transmission powers a rotating pump shaft 18 and an air compressor 13.
In other firefighting pump transmission systems an opening is provided on the gearcase or housing of a primary transmission to receive a specially designed auxiliary transmission or device. A specially designed PTO device is used to couple the primary transmission to the auxiliary device. The auxiliary system may be equipped with a sliding clutch gear to engage or disengage a driven device. For instance, an auxiliary device such as a booster pump or compressor may typically be mounted to the housing or closely coupled to the housing of a firefighting pump transmission. An example of such a system is the model LDMH pump manufactured by W.S. Darley & Company, Chippewa Falls, Wis.